Michael Jackson's scalp getting burnt while filming a commercial was the biggest turning point in his life, insists his friend David Gest.

The late singer's hair was accidentally set on fire as he was making an advert for Pepsi in 1984, and Gest believes the subsequent treatment Jackson received following the accident sent the star - who died of acute Propofol intoxication in June 2009 - into a downward spiral.

Speaking on BBC Breakfast, Gest said: "When he started his solo career and he left Motown, when he did Off The Wall, Bad and Thriller, he was in complete control of everything he did. He was in charge.

"It was that accident; when you get a head concussion it changes your life because you get addicted to drugs to get rid of all the pain."

As a result of the accident, Jackson was rushed to hospital and treated for second degree burns. He likely had plastic surgery soon after to hide his hair loss and altered his appearance many times over the rest of his life, with Gest claiming he had to undergo 'ballooning' procedures, a method of alopecia reduction for surgical hair restoration, up until he died.

He added: "He never got over that. He had ballooning, ballooning is when you expand the scalp, until the day he died he was being ballooned."

Michael's brother, Tito - who also appeared on the show - said Michael was "dropped something like 40 or 50 feet from the stage at one of his shows," which also had a bad effect on him.

Gest's documentary, Michael Jackson: The Life of an Icon, will have its London premiere on Wednesday, and is available to buy on DVD now.